I was just wondering, was the OP question actually answered?
What is the best economical option for a precision frequency reference?
With my experience so far, the FE5680B seems to be it.
What is the easiest to use and have running and have accurate without worrying about being off because of age drift?
IMHO the bg7tbl GPSDO on ebay, any flavor, is the best bet.
I am the OP. I think the answer depends on what your specific needs are. They all stay accurate without drift - that's what the GPS is there for. Here is a breakdown of how I see it:
BG7TBL / 2014-12-09 -
Pros: Smallest unit, good sensitivity on GPS receiver.
Cons: Small frequency error. OCXO has a high failure rate in first 30 days. No management interface. Produced by someone who is semi-anonymous and not able or willing to answer questions about his product. No software to monitor. GPS chip is a UBlox non-timing chip, which has more jitter than their equivalent timing chips (like the one used in the Huawei).
Huawei/BG7TBL 2015-07-08 (Star4+ board)
Pros: Excellent OCXO, Good management interface, excellent GPS sensitivity using UBlox timing application-specific GPS receiver module, coolest running unit. Simple mod to expose second 10M output (square wave)
Cons: Requires minor change (solder two wires) to fix management interface mis-wiring from BG7TBL. Limited availability now it seems. No software to monitor.
"TRIMBLE"/BG7TBL 2015-07-17 -
Pros: Good management interface.
Cons: Insensitive GPS receiver. OCXO quality was on the low end (but still not bad). No software to monitor.
Lucent KS24361
Pros: Great management interface compatible with Z38XX software. Ties with Huawei for quality of output.
Cons: Big (two units, but can be hacked into one unit with a special cable and mod to expose the 10Mhz signal). Generates a ton of heat compared to all but the BG7TBL unit which is similarly hot. Poor sensitivity on GPS receiver. Crazy DB9 power connectors with funky latch. RS422 interface instead of RS232. 15 MHz primary output instead of 10. It has 10 MHz output, but it's reportedly relatively poor quality compared to the 15Mhz.
So personally, I prefer the Huawei/Star4+ board, with or without the BG7TBL strap-on hardware. My second choice would probably be the BG7TBL/2014-12-09 unit, because the frequency error isn't important to me, and it does make a nice compact unit and has good GPS sensitivity. My third choice would be the Lucent.